This invention relates generally to overcoming the problem of fog production during or as a result of vaporization of liquefied gases, as for example liquefied natural gas (LNG), nitrogen, oxygen, and ethylene.
Liquefied gases (for example those listed above) frequently require heating to convert the liquid back into gas, for use. Conventionally, this heating process is referred to as vaporization and the devices employed as vaporizers.
One of the most common and least expensive sources of heat is ambient air. Many of the liquefied gases are stored at temperatures below the freezing point of water. Thus heat exchanges with ambient air can produce large amounts of cold air and, in certain atmospheric conditions, a ground fog. Most applications are small enough that the fog can be readily dissipated, but some are so large that the fog forms a hazard or nuisance. A good example is a receiving and re-gasification terminal for LNG (Liquefied Natural Gas). These facilities can have heat requirements in excess of 500,000,000 BTU/hr. Traditional methods of vaporization take a portion of the product stream, and burn it to produce the required heat. This can consume up to about 3% of the vaporized product and represents a substantial operating cost.
Additionally, new restrictions on NOx reduction have made combustion vaporization more difficult to live within the air pollution requirements at the re-gasification sites. The use of ambient air in conjunction with conventional heating systems has enormous appeal from both an economic and air pollution standpoint, if the fog issues can be overcome.